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Jim Colegrove at Trek

Jim Colegrove portrait
Peter Stuart
14 Sep 2015

With an intimate knowledge of carbon fibre, Trek's senior composites engineer has played a big part in making bikes what they are today.

Cyclist: How did you get started at Trek?

Jim Colegrove: In 1990 Trek wanted to build composite parts in-house after a disastrous start using a separate company to build the 5000 frame. That was a made-in-one-piece back in 1988 and 1989. Terrible failure – we got virtually every one back. Key people realised carbon fibre was the future, and I was hired to help bring the manufacturing into this facility. I came from a small engineering firm in Salt Lake City that worked with aerospace clients – Boeing, Lockheed, Northrop, those kind of companies. Jackson Street was where Trek started, which was a red barn in downtown Waterloo [Wisconsin]. Trek started brazing frames there in 1976. Now it houses the CNC tool machining facility to cut all the moulds we use to make our parts. 

Cyc: Do the aerospace and military industries use much higher-quality carbon than is used in bikes?

JC: The material that the aerospace and defence industries use is nearly identical to the material that the recreational industries use. What is generally missing is certification and also verification of manufacture. We use a lot of different fibres, some of which are the same as those used for top-end military and aerospace purposes. M60J, for instance, is an ultra high-modulus Toray fibre. The last time I looked, it was something north of $900 a pound [approx £1,270 per kilo]. Some of these high and ultra-high modulus materials are classified as strategic materials, and that means they are only available in certain NATO countries because you can make weapons out of them. We use almost all the fibres out there, whether it’s Toray, Mitsubishi, Hexcel, Cytec. You name it, we’re using it. 

Cyc: What’s special about the way Trek does things?

JC: One of the key things is how we mistake-proof the process. Any time you put a human into the mix there is the possibility for mistakes. All of our products over the last five or six years have gone through our validation lab, which is a sort of mock factory. We bring in our documentation specialists who tell our operators what they’re going to do. We bring those operators into the validation lab and train them so we have a seamless transition. We try to develop things in a way that will transition well into production. Because when you take things out of a lab environment and into production there are always small glitches – things you didn’t think about.

Cyc: How do you juggle the demands of design and research in the United States while doing a great deal of your production in the Far East?

JC: What I think is really key is that what is learned here is propagated over to our Asian partners. One of the things I feel sets us apart is the fact that we are deeply embedded in manufacturing. We build all top-end Project One bikes in Wisconsin, and we know the factory is expensive, but if we don’t do it here we lose that direct connection to building the product. We can design a beautiful frame and ship it over to somebody but we’d have no idea if what we have designed is buildable and if it is buildable in a good, unique way.

Jim Colegrove interview

Cyc: How does the composite nature of carbon fibre influence frame design?

JC: There’s sort of a ‘black aluminium’ theory where designers treat carbon as if it were a regular isotropic metal. So, some of the FEA [Finite Element Analysis] used in bike design is done by inputting aluminium as the material and designing the tubes purely on the effect of certain wall thickness. That’s not true composite FEA. That’s fine for getting an acceptable product, but if we want to dial in the type of ride performance that we’re chasing at the top, we need to do things properly. In our design you can see the number of plies and where we’ve placed them, and all of that is driven by our analysis.

Cyc: How has the trend for improved aerodynamics affected the way you approach design?

JC: Aerodynamics has really caused a dilemma for us. Aero tube shapes tend to require larger surface areas, and whenever you add more surface area to any part there’s more weight, right? Also, either it’s so harsh on the rider because it’s such a tall section, or it’s so narrow that the bike is all over the place [because of lateral flex]. That’s where our analysis really comes into play. First of all we analyse the shape from an aerodynamic standpoint, and then once we know that we have a certain aerodynamic shape, then we start plugging that into FEA. If those two aren’t going to play together then we have to add material to meet the aerodynamics, but then the bike is going to be too heavy – that’s not going to be acceptable. So we constantly converge on the best solution.

Cyc: Carbon fibre bikes are half carbon fibres and half resin. How important is the resin?

JC: Very. We don’t talk a lot about it, but we are constantly working with different resins. It’s a composite material – carbon fibre does the work and the epoxy resin holds the fibres in position. So if the resin isn’t doing its job holding the fibres in position, you’re not going to get any real performance out of the fibres. We formed a stronger relationship with [carbon fibre producer] Hexcel because it has a wide range of resins that have unique and special properties. The problem is it further complicates an already complicated concept. There is so much jargon floating around – is it a T700 or a T800 or an IM7 or an IM8, what’s the moduli, strength and elongation? It’s confusing enough without getting into resins. 

Cyc: Carbon sometimes has a bad reputation for having a limited life. Is this true?

JC: People seem concerned about carbon fibre because it’s an unknown. People have grown up with steel and aluminium. Every material has a fatigue life. Take a steel paperclip and bend it a hundred times it will probably break. Do the same with aluminium, and it will probably break in half the time because aluminium is not as good in fatigue as steel. Composites, in general, have an infinite fatigue life. But that depends on the carbon fibre use, the resin use and how well it was processed. In other words, are there a lot of voids in the laminate? Because voids will kill a composite very quickly. That was common years ago, but not any more. This, again, is where complete control of materials, process and engineering play an important role. If you take control of all of that, we can definitively say that a bike you buy today, you can ride for your lifetime, and it will not degrade over that lifetime.

Cyc: Are you on the hunt for new and extraordinary materials?

JC: We’re always looking for new material forms. Graphene is one of those, but it’s still being developed. There are manufacturers of nano-graphene platelets, so you can get it already, but it’s very expensive. The biggest thing for us is that unless we can see benefit in the composite, we’re not completely sold. If we can figure out some way of getting graphene or carbon fibre nanotubes to create the long strings like we have for current carbon fibre, oh my gosh, the stiffness, the strength, the weight would be unbelievable.

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